Fix Virtual Machine Import, ensure that the vCPU Attribute is an integer

[sirtux]

Closes #85

When importing the data, the vCPU value, which is due to the json a string, is first casted to a float, and than to an int.

[glennmatthews]

Looks reasonable as a workaround for a feature that was added in NetBox 2.11. Longer-term it might be desirable to port that feature to Nautobot :-).

My only suggestion here might be to add a logger.warning call in the case where this results in rounding or data loss (e.g. converting a NetBox 0.5 value to a Nautobot 0)

[sirtux]

Hmm, not sure if a warning makes much sense, since as far as I know, there is no virtualization solution which allows assignment of partial cores, it should always be an integer, so it believe nautobot is completly right here.